Integrated modelling for urban surface water exceedance flows

The basis for an integrated modelling approach to pluvial exceedance flooding is described together with the principal challenges and uncertainties associated with the extraction and interpretation of the terrestrial Lidar (light detection and ranging) data survey used to derive high-resolution digital elevation modelling (DEM) of the urban surface micro-topography and morphology. The terrestrial Lidar DEM has been developed within an integrated sewer/overland flow modelling approach using a coupled geographic information system (GIS)-based one-/two-dimensional framework. The advantages of mobile ground-based Lidar over airborne survey systems are examined in terms of the definition of appropriate grid cell sizes and scaling for the accurate quantification of flood distribution, depths and flowpaths as required for the identification of ‘critical drainage areas'. The performance outcomes of an innovative sustainable urban drainage (Suds) selection tool (Sudsloc) are also examined in terms of varying DEM conditions and the accuracy of the predicted flood depths and distributions. The integrated modelling application provides a flexible and robust risk assessment tool for predicting and managing pluvial flooding in urban catchments